1. Field of the Invention
The present invention relates to a fastening device and more particularly, to a fastener for joining metal plate members that is easy and inexpensive to manufacture.
2. Description of the Related Art
When fastening plate members together, a positioning screw formed of a knob, a ring and a screw nail is usually used. During installation, the screw nail and the ring are secured to the first plate member, and then the knob is rotated to drive the screw nail into the second plate member, and then a hand tool is used to fasten tight the screw nail, affixing the first and second plate members together. This plate member joining method can be used in a machine tool to join plate members together.
The power drive and speed-adjustment unit of a machine tool are generally provided inside the housing. To facilitate repair of a machine tool or adjustment of the output speed of a machine tool, a detachable plate member is usually provided at the housing of the power drive or speed-adjustment unit. Screw bolts are commonly used to fasten the movable plate member to the housing. When unfastening screw bolts to dismount a movable plate member from the housing, the associating lock nuts may fall from the screw bolts.
There is known a fastener comprised of a cap, a screw, a spring member, a mounting socket and a locknut for joining two metal plate members together. The fastener is to be picked up for installation manually. During installation, hold the cap with the hand to move the fastener into alignment with the mounting through hole on the first metal plate member, and then insert the front (bottom) end of the mounting socket into the mounting through hole to have a mounting flange of the mounting socket be bonded to the top wall of the first plat member with a solder paste. Picking up the fastener for installation manually wastes much time and labor. For automatic installation by a mounting system, a Teflon ring may be used with the fastener. The Teflon ring is inserted into the bottom hole of the mounting socket and forced into friction engagement with the periphery of the bottom end of the screw to lock the cap, the screw and the mounting socket, allowing the fastener to be picked up by a mounting system for quick installation. Immediately after bonding of the mounting socket to the first plate member, the cap and the screw must be rotated to force the Teflon ring away from the mounting socket and the first plate member so that the cap can be lowered relative to the mounting socket and the first plate member for enabling the screw to be driven into the second plate member.